Embodiments relate generally to chilled water systems used in air conditioning systems, and more particularly to energy management of a chilled water system.
A common method to reduce chilled water system energy usage is to adjust (i.e., modify the operating set point) the chilled water supply temperature upwards and/or the condenser water supply temperature downwards (in systems having a water cooled condenser). Doing so can reduce overall energy usage. However, if one adjusts the temperatures too far, then energy usage can increase, rather than decrease. Existing chilled water energy management systems incorporate equipment modeling, and/or algorithms based in part on equipment modeling, to predict what chilled water and/or condenser water supply temperatures will result in the lowest energy use (expressed as efficiency in kW/ton). Modeling relies on specific chiller, pump, and fan power curves for the equipment in the chilled water plant. Each plant requires such custom data, and only with this data can the algorithms find the lowest energy usage throughout the day.
In any method dependent on modeling, finding the optimal efficiency is dependent on specific equipment data applied to a pristine system design. This locks a specific chilled water system to an ideal energy model. But chilled water systems do not remain pristine. They can change over time. The systems age, pipes foul and various components may be replaced. As the actual operating parameters depart from the model, the ability to reduce energy usage and improve efficiency is degraded.